This invention relates to a fluorescent lamp device which uses curved fluorescent lamps.
A fluorescent lamp device has recently been developed which has an outer case accommodating some fluorescent lamps bent in a U-shape, a W-shape or a saddle-shape, as well as operating circuit parts such as a stabilizer, a glow switch starter, a capacitor, etc., and a base for use with an incandescent lamp is attached to the outer case. Interchangeable with an incandescent lamp, this kind of fluorescent lamp device is becoming increasingly popular as an energy-saving light source, and development is now underway to make it smaller in size and greater in output.
The ordinary method for making a lamp more compact is to reduce the diameter of the glass tube constituting the fluorescent lamp and to reduce the curvature of the bent portions of the glass tube. Reducing the curvature is done in order to bring one straight glass tube part as close to another as possible, or even in contact with each other, in some cases.
In order to give the lamp a greater output, it is necessary to elongate its discharge channel as much as possible within the limited space. Making the glass tube smaller in diameter as well as reducing the curvature of the bent portions also makes the lamp compact.
However, if the glass tube is made smaller in diameter, its wall temperature will rise higher, even if the inut to the fluorescent lamp is the same. In other words, if the glass tube is reduced in diameter, the surface area of the glass tube, which determines the heat radiation efficiency of the lamp, becomes smaller. Therefore, the temperature of the glass tube wall rises, even if the input governing the lamp's calorific value is the same.
Also, since the curvature of the bent portions is reduced, the glass tubes can be placed closer to one another. However, this means that glass tubes which must radiate heat effectively, will be located close to one another glass. These conditions will lower the heat discharge efficiencies of the individual glass tubes, and excessive heat will be generated.
The temperature rise in the glass tube walls induces yet another problem: the fluorescent substance applied to the internal surface of the glass tubes deteriorates more quickly and the life of the fluorescent lamp is shortened. Further, another problem raised is that the mercury vapor pressure in the fluorescent lamp becomes harder to control due to this temperature rise.